The Portable Operating System Interface
The Portable Operating System Interface (POSIX) standardization effort used to be run by the POSIX standards committee. During a major overhaul of the names and numbers used to refer to this project, PASC (Portable Applications Standards Committee) came into being. So now the POSIX standards are written and maintained by PASC, just so that you know.
POSIX was designed as a standard environment to enable the portability of applications software and to some extent people. This portability of applications software is achieved through the specification of a set of services that every POSIX conforming application can expect to exist on a conforming platform.
A set of software standards being developed by the IEEE POSIX Working Group, to allow applications to be written to a single target environment in which they can run unchanged on a variety of systems. The POSIX specifications define characteristics for operating systems, DBMS, data interchange, network services, user interface, and programming interfaces. Several vendors plan to make their operating systems POSIX-compliant.